A concern of today's emerging digital consumer electronics products is the ability to access a “plaintext” (i.e., ‘in the clear’) digital bitstream, thereby permitting one to make unauthorized digital copies of the bitstream. The National Renewable Security Standard (NRSS) (EIA-679) developed by the Electronic Industries Alliance provides a means for employing renewable security in connection with digital consumer electronics (CE) devices, for example, digital television receivers (DTVs), digital video cassette recorders (DVCRs) and set-top boxes (STBs). Renewable security allows for the development of conditional access systems that can be replaced, upgraded or recovered with minimum cost and effort.
Typically, a service provider will scramble the signal before it is transmitted or broadcast. A conditional access (CA) device (e.g., an NRSS smart card) may be used to descramble the signal and route it to the host device. However, a problem with the NRSS architecture is that the audio/visual (A/V) stream is sent to the host device (for example, a display device or a set top box) from the smart card needs to be protected. That is, the A/V stream needs to be scrambled when it leaves the CA device. Otherwise, a person can monitor this line and use a data capturing device to record all the data.
Thus, there is presently a need for a conditional access system which effectively protects the transmission channel from a conditional access device (e.g., smart card) to a host and/or display device (e.g., DTV, STB, etc.).